Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Uneven, Uneven, Gemstones of the world (2001) More from other references
MgCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references